Mesa (main): nir/algebraic: fix imod by negative power-of-two

[GitLab Mirror]

Module: Mesa
Branch: main
Commit: ec4b425f596d5bbe4c2401b9cfc08d7c9eaa36b0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ec4b425f596d5bbe4c2401b9cfc08d7c9eaa36b0

Author: Rhys Perry <pendingchaos02 at gmail.com>
Date:   Wed Jul 21 17:06:30 2021 +0100

nir/algebraic: fix imod by negative power-of-two

If "a" is a multiple of "b", then the result would have been "b" instead
of 0.

No fossil-db changes.

Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
Fixes: 0ef5f3552f6 ("nir: add strength reduction pattern for imod/irem with pow2 divisor.")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12039>

---

 src/compiler/nir/nir_opt_algebraic.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index f2bf852ea8b..32547027679 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -114,9 +114,9 @@ optimizations = [
    (('idiv', a, '#b(is_neg_power_of_two)'), ('ineg', ('imul', ('isign', a), ('ushr', ('iabs', a), ('find_lsb', ('iabs', b))))), '!options->lower_bitops'),
    (('umod', a, '#b(is_pos_power_of_two)'),    ('iand', a, ('isub', b, 1))),
    (('imod', a, '#b(is_pos_power_of_two)'),    ('iand', a, ('isub', b, 1))),
-   (('imod', a, '#b(is_neg_power_of_two)'),    ('ior', a, b)),
-   (('irem', a, '#b(is_pos_power_of_two)'),    ('bcsel', ('ige', a, 0), ('iand', a, ('isub', b, 1)), ('ior', a, ('ineg', b)))),
-   (('irem', a, '#b(is_neg_power_of_two)'),    ('bcsel', ('ige', a, 0), ('iand', a, ('inot', b)), ('ior', a, b))),
+   (('imod', a, '#b(is_neg_power_of_two)'),    ('bcsel', ('ieq', ('ior', a, b), b), 0, ('ior', a, b))),
+   (('irem', a, '#b(is_pos_power_of_two)'),    ('bcsel', ('ige', a, 0), ('iand', a, ('isub', b, 1)), ('imod', a, ('ineg', b)))),
+   (('irem', a, '#b(is_neg_power_of_two)'),    ('bcsel', ('ige', a, 0), ('iand', a, ('inot', b)), ('imod', a, b))),
 
    (('~fneg', ('fneg', a)), a),
    (('ineg', ('ineg', a)), a),